CN109444998B - Super surface focusing lens - Google Patents
Super surface focusing lens Download PDFInfo
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- CN109444998B CN109444998B CN201811453582.3A CN201811453582A CN109444998B CN 109444998 B CN109444998 B CN 109444998B CN 201811453582 A CN201811453582 A CN 201811453582A CN 109444998 B CN109444998 B CN 109444998B
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Abstract
The invention discloses a super-surface focusing lens. Disposing a first antenna layer on a first side of a first dielectric layer; a first side of the transparent conductive oxide layer is disposed on a second side of the first dielectric layer; the second antenna layer is arranged inside the second dielectric layer; a second dielectric layer disposed on the second side of the transparent conductive oxide layer; the reflectivity of the transparent conductive oxide layer to incident light of the first wave band is greater than or equal to 70%, and the incident light belonging to the first wave band can be reflected, so that a reflection focusing function is realized; the transparent conductive oxide layer has a transmittance of 75% or more for incident light in the second wavelength band, and allows incident light in the second wavelength band to pass therethrough, thereby realizing a transmission focusing function. The invention can focus two beams of light belonging to different wave bands in different scattering spaces, solves the technical problem that the super-surface focusing lens can only work in a single wavelength or the same wave band, and expands the application range of the super-surface focusing device in the aspect of multi-wavelength.
Description
Technical Field
The invention relates to the technical field of optical devices, in particular to a super-surface focusing lens.
Background
The metasurface (Metasurfaces) is a two-dimensional metamaterial, has attracted wide attention in recent years due to its extraordinary light manipulation capability and the advantages of on-chip integration, and has wide applications in beam deflection, beam splitting, beam transformation, focusing, holographic imaging, polarization conversion, surface plasmon excitation, and the like. Among the above-mentioned various functions, focusing is one of the most popular research directions. At this time, the super surface can realize the focusing action of the lens, and is also called a planar super lens because the super surface itself is a two-dimensional ultra-thin structure. Compared with the defects of large volume, difficult processing, incapability of integration and the like of the traditional lens, the focusing lens based on the super surface has the advantages of small volume, thinness and easiness in integration with the existing optoelectronic device, and has important application values in the aspects of holography, imaging, spectroscopy, photoetching, laser processing and the like.
However, the super-surface focusing lens reported in the prior art can only work at a single wavelength or work at the same wavelength band. That is, even if they have a focusing effect on light of a plurality of different wavelengths, these wavelengths all belong to the same wavelength band, for example, all belong to the visible, all belong to the infrared, or all belong to the microwave band. These limitations have limited the wide use of super-surface focusing lenses.
Disclosure of Invention
The invention provides the super-surface focusing lens, solves the technical problem that the super-surface focusing lens in the prior art can only work at a single wavelength or work at the same waveband, and enlarges the application range of the super-surface focusing device in the aspect of multi-wavelength.
The invention provides a super-surface focusing lens, comprising: a first antenna layer, a first dielectric layer, a transparent conductive oxide layer, a second antenna layer, and a second dielectric layer; the first antenna layer is disposed on a first side of the first dielectric layer; a first side of the transparent conductive oxide layer is disposed on a second side of the first dielectric layer; the second antenna layer is embedded inside the second dielectric layer; the second dielectric layer is disposed on a second side of the transparent conductive oxide layer; the transparent conductive oxide layer has a reflectance of 70% or more with respect to incident light in a first wavelength band and a transmittance of 75% or more with respect to incident light in a second wavelength band.
Further, the first antenna layer and/or the second antenna layer is a square open loop antenna, a V-shaped open loop antenna, or a circular open loop antenna.
Further, a first super surface structure unit is composed of the first antenna layer, the first dielectric layer and the transparent conductive oxide layer; forming a second super-surface structure unit by the second antenna layer and the second dielectric layer; the number of the first super-surface structure units is at least 1 along the direction of the magnetic field component of the light wave, and at least 3 along the direction of the electric field component of the light wave; the number of the second super-surface structure units is at least 1 along the direction of the magnetic field component of the light wave, and at least 3 along the direction of the electric field component of the light wave.
Further, the material of the transparent conductive oxide layer is transparent and conductive oxide.
Further, the transparent, electrically conductive oxide is indium tin oxide or zinc gallium oxide.
Further, the material of the first antenna layer and/or the second antenna layer is metal.
Further, the metal is gold, silver, aluminum or copper.
Further, the material of the first dielectric layer and/or the second dielectric layer is an insulator material or a semiconductor material.
Further, the insulator material is silicon dioxide, aluminum oxide or magnesium difluoride.
Further, the semiconductor material is indium phosphide, gallium arsenide, or gallium nitride.
One or more technical schemes provided by the invention at least have the following technical effects or advantages:
disposing a first antenna layer on a first side of a first dielectric layer; a first side of the transparent conductive oxide layer is disposed on a second side of the first dielectric layer; the second antenna layer is arranged inside the second dielectric layer; a second dielectric layer disposed on the second side of the transparent conductive oxide layer; the reflectivity of the transparent conductive oxide layer to the incident light of the first wave band is greater than or equal to 70%, so that the incident light belonging to the first wave band can be reflected, and the reflection focusing function is realized; the transparent conductive oxide layer also has a transmittance of 75% or more for incident light of the second wavelength band, thereby allowing incident light belonging to the second wavelength band to pass therethrough, and realizing a transmission focusing function. The first waveband and the second waveband are different wavebands. Therefore, the invention can focus two beams of light belonging to different wave bands in different scattering spaces, and simultaneously utilizes the reflection space and the transmission space, thereby solving the technical problem that the super-surface focusing lens in the prior art can only work in a single wavelength or the same wave band, and expanding the application range of the super-surface focusing device in the aspect of multi-wavelength.
Drawings
FIG. 1 is a schematic structural diagram of a super-surface focusing lens according to an embodiment of the present invention;
FIG. 2 is a cross-sectional view of a dual-wavelength super-surface focusing lens of a specific structure provided in an embodiment of the present invention;
FIG. 3 is a schematic structural view of the first super-surface of FIG. 2;
FIG. 4 is a schematic structural view of the second super-surface of FIG. 2;
FIG. 5 is a schematic perspective view of an upper structure unit in a super-surface focusing lens according to an embodiment of the present invention;
FIG. 6 is a top plan view of an upper structure unit in a super-surface focusing lens according to an embodiment of the present invention;
FIG. 7 is a schematic perspective view of a lower structural unit of a super-surface focusing lens according to an embodiment of the present invention;
FIG. 8 is a top plan view of a lower structural unit in the super-surface focusing lens provided in the embodiment of the present invention;
FIG. 9 is a field intensity distribution diagram of an incident light with a wavelength of 2365nm incident on a super-surface focusing lens along a negative z direction according to an embodiment of the present invention;
FIG. 10 is a normalized intensity distribution curve at the focal point cross-sectional line after incident light with a wavelength of 2365nm is reflectively focused in an embodiment of the present invention;
FIG. 11 is a field intensity distribution diagram of incident light with a wavelength of 650nm incident on a super-surface focusing lens along the negative z-direction according to an embodiment of the present invention;
FIG. 12 is a normalized intensity distribution curve at the focal point transversal line after incident light with a wavelength of 650nm is reflectively focused according to an embodiment of the present invention.
The antenna comprises a first antenna layer, a first dielectric layer, a transparent conductive oxide layer, a second dielectric layer and a transparent conductive oxide layer, wherein the antenna comprises 1-the first antenna layer, 2-the first dielectric layer, 3-the transparent conductive oxide layer, 4-the second dielectric layer and 5-the second antenna layer.
Detailed Description
The embodiment of the invention provides the super-surface focusing lens, solves the technical problem that the super-surface focusing lens in the prior art can only work at a single wavelength or work at the same waveband, and expands the application range of a super-surface focusing device in the aspect of multi-wavelength.
In order to solve the above problems, the technical solution in the embodiments of the present invention has the following general idea:
disposing a first antenna layer on a first side of a first dielectric layer; a first side of the transparent conductive oxide layer is disposed on a second side of the first dielectric layer; the second antenna layer is arranged inside the second dielectric layer; a second dielectric layer disposed on the second side of the transparent conductive oxide layer; the reflectivity of the transparent conductive oxide layer to the incident light of the first wave band is greater than or equal to 70%, so that the incident light belonging to the first wave band can be reflected, and the reflection focusing function is realized; the transparent conductive oxide layer also has a transmittance of 75% or more for incident light of the second wavelength band, thereby allowing incident light belonging to the second wavelength band to pass therethrough, and realizing a transmission focusing function. The first waveband and the second waveband are different wavebands. Therefore, the embodiment of the invention can focus two beams of light belonging to different wave bands in different scattering spaces, and simultaneously utilizes the reflection space and the transmission space, thereby solving the technical problem that the super-surface focusing lens in the prior art can only work in a single wavelength or the same wave band, and expanding the application range of the super-surface focusing device in the aspect of multi-wavelength.
For better understanding of the above technical solutions, the following detailed descriptions will be provided in conjunction with the drawings and the detailed description of the embodiments.
Referring to fig. 1, a super-surface focusing lens provided by an embodiment of the present invention includes: a first antenna layer 1, a first dielectric layer 2, a transparent conductive oxide layer 3, a second antenna layer 5, and a second dielectric layer 4; the first antenna layer 1 is disposed on a first side of the first dielectric layer 2; a first side of the transparent conductive oxide layer 3 is disposed on a second side of the first dielectric layer 2; the second antenna layer 5 is embedded inside the second dielectric layer 4; a second dielectric layer 4 is disposed on the second face of the transparent conductive oxide layer 3; the transparent conductive oxide layer 3 can have a reflectance of 70% or more with respect to incident light of a first wavelength band and a transmittance of 75% or more with respect to incident light of a second wavelength band. The first waveband and the second waveband are different wavebands.
The structures of the first antenna layer 1 and the second antenna layer 5 are specifically described, and the first antenna layer 1 and/or the second antenna layer 5 are/is a square open loop antenna, a V-shaped open loop antenna or a circular open loop antenna, so that full coverage of a 2 pi phase can be realized, and the requirement on focused phase distribution is met.
In this embodiment, the first antenna layer 1 and the second antenna layer 5 may adopt the same open-loop antenna shape, or may adopt different open-loop antenna shapes.
Specifically, the structure of the super-surface focusing lens provided by the embodiment of the invention is described, wherein a first super-surface structure unit is composed of a first antenna layer 1, a first dielectric layer 2 and a transparent conductive oxide layer 3; a second super-surface structure unit is formed by the second antenna layer 5 and the second dielectric layer 4; the number of the first super-surface structure units is at least 1 along the direction of the magnetic field component of the light wave, and at least 3 along the direction of the electric field component of the light wave; the number of the second super-surface structure units is at least 1 along the direction of the magnetic field component of the light wave, and at least 3 along the direction of the electric field component of the light wave.
In this embodiment, the structure composed of the plurality of first super-surface structure units is a first super-surface, and the structure composed of the plurality of second super-surface structure units is a second super-surface.
The material of the transparent conductive oxide layer 3 is specifically described, and the material of the transparent conductive oxide layer 3 is a transparent oxide having conductivity, which has a wide application range, good conductivity, and unique optical properties, and can produce a high reflectance for light of a first wavelength band and a high transmittance for light of a second wavelength band.
In this embodiment, the transparent and conductive oxide is indium tin oxide or zinc gallium oxide.
Specifically, the materials of the first antenna layer 1 and the second antenna layer 5 are described, and the material of the antenna in the first antenna layer 1 and/or the second antenna layer 5 is metal.
In this embodiment, the metal is gold, silver, aluminum, or copper. Here, it should be noted that the same material may be used for the first antenna layer 1 and the second antenna layer 5, or different materials may be used. The material of the second antenna layer 5 is the same as that of the second dielectric layer 4 except for the open-ended resonant loop antenna (which is made of metal).
Specifically, the materials of the first dielectric layer 2 and the second dielectric layer 4 are described, and the material of the first dielectric layer 2 and/or the second dielectric layer 4 is an insulator material or a semiconductor material.
In the present embodiment, the insulator material is silicon dioxide, aluminum oxide, magnesium difluoride, etc., and the semiconductor material is indium phosphide, gallium arsenide, gallium nitride, etc.
Here, the materials of the first dielectric layer 2 and the second dielectric layer 4 may be the same or different.
The embodiment of the invention provides a super-surface focusing lens with a specific structure, which specifically comprises the following components:
referring to fig. 2, 3 and 4, an xyz coordinate system is shown in fig. 2, where the incident direction of light (the direction of wave vector K) is along the negative z-axis direction, the direction of the electric field component of light wave (the direction of electric field E) is along the x-axis direction, and the direction of the magnetic field component of light wave (the direction of magnetic field strength H) is along the y-axis direction. Specifically, the number of the first super-surface structure units is 32 in total along the x-axis direction (i.e. the direction of the electric field E), the total length is 6400nm, and the 32 first super-surface structure units are periodically arranged along the y-axis direction (i.e. the direction of the magnetic field intensity H), and the period is 800 nm. The number of the second super-surface structure units is 128 along the direction of the x axis (namely the direction of the electric field E), the total length is 6400nm, and the 128 second super-surface structure units are periodically arranged along the direction of the y axis (namely the direction of the magnetic field intensity H), and the period is 200 nm.
It should be noted that, according to different size design requirements, the correspondence relationship between the first super-surface structure unit and the second super-surface structure unit can also be any number of square multiples, such as 4, 9, 25, etc., and is not limited to 16.
In an embodiment of the invention we introduce a transparent conductive oxide (indium tin oxide) material consisting of 90% by weight indium oxide (In)2O3) And 10% tin oxide (SnO)2) The composition is an oxide semiconductor with the band gap width exceeding 3.5eV, and visible light and near infrared light cannot excite electronic transition, so that the indium tin oxide has better optical transparency in the band range. At the same time, the indium tin oxide resistance is higher due to the higher doping concentrationThe refractive index is relatively low and exhibits negative refractive index properties in the infrared band. Therefore, indium tin oxide has high reflectivity in the infrared band like metal, and exhibits a transparent property in visible light.
Referring to fig. 5 and 6, the first super surface structure unit (upper structure unit) includes a first antenna layer 1 (upper antenna layer), a first dielectric layer 2 (upper dielectric layer), and a transparent conductive oxide layer 3. The first antenna layer 1 is disposed on the upper surface of the first dielectric layer 2, and is configured as a square open-loop antenna, and the first dielectric layer 2 is disposed on the upper surface of the transparent conductive oxide layer 3. The material of the first dielectric layer 2 is silicon dioxide, the material of the transparent conductive oxide layer 3 is indium tin oxide, and the material of the first antenna layer 1 is metal. Preferably, the metal material is gold.
Wherein the thickness d of the upper antenna layer1150nm, thickness d of the upper dielectric layer2220nm, thickness d of the transparent conductive oxide layer 33Is 160 nm. Meanwhile, the first super-surface structure unit is of a square structure with the side length T1Is 800 nm. Length L of square split resonant loop antenna1Is 425nm and has a width W125nm and an arm length of S1. The square split ring antennas with different split sizes can produce different electromagnetic response characteristics, i.e., different phase change amounts to the reflected light. According to the steering mechanism of the symmetrical split-ring antenna, the phase of the cross polarization component (y-polarized light) of the incident x-polarized light is changed. When the opening is at the lower left corner of the antenna, the length value S of the arm is adjusted1A phase shift of 0-pi may be provided for the cross-polarized light component; after the antennas are rotated by 90 degrees clockwise, pi phase shift can be introduced again, and 0-2 pi phase response coverage is realized, so that the primary condition that the super surface realizes perfect control on electromagnetic waves is met.
When the wavelength of incident light is 2365nm, table 1 shows the arm length S corresponding to the square open loop antenna with 32 upper structural units when the phase change amount of the reflected light satisfies the parabolic phase distribution1(in Table 1, when S1When the number is positive, the opening is at the upper left corner; s1When it is negative, generationTable open at the lower left corner, whose absolute value represents the arm length value). The x coordinate of the central position of the upper structural unit with the number of 1 is-12.4 μm, and the central positions of the following upper structural units are sequentially increased by 0.8 μm. The upper structural units numbered 1, 2 and … … 32 are sequentially arranged along the x-axis direction (namely the x direction) to form a whole row, and the total length of the whole row is 6400 nm; a plurality of the whole rows are periodically arranged along the direction vertical to the electric field (namely the y direction) and form a first super surface, the arrangement period is 800nm, and the period number N is more than or equal to 2.
| Upper structure unit numbering | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| S1(nm) | 0.0 | 113.1 | 229.8 | -10.6 | -120.2 | -215.7 | -304.0 | 0.0 |
| Phase (rad) | 3.32 | 4.40 | 5.42 | 0.10 | 1.01 | 1.85 | 2.63 | 3.34 |
| Upper structure unit numbering | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 |
| S1(nm) | 63.6 | 127.3 | 183.8 | 233.3 | 268.7 | 300.5 | 318.2 | 330.0 |
| Phase (rad) | 3.98 | 4.54 | 5.03 | 5.44 | 5.77 | 6.02 | 6.19 | 6.27 |
| Upper structure unit numbering 1 | 7 | 18 | 19 | 20 | 21 | 22 | 23 | 24 |
| S1(nm) | 330.0 | 318.2 | 300.5 | 268.7 | 233.3 | 183.8 | 127.3 | 63.6 |
| Phase (rad) | 6.27 | 6.19 | 6.02 | 5.77 | 5.44 | 5.03 | 4.54 | 3.98 |
| Upper structure unit numbering | 25 | 26 | 27 | 28 | 29 | 21 | 31 | 32 |
| S1(nm) | 0.0 | -304.0 | -215.7 | -120.2 | -10.6 | 229.8 | 113.1 | 0.0 |
| Phase (rad) | 3.34 | 2.63 | 1.85 | 1.01 | 0.10 | 5.42 | 4.40 | 3.32 |
Table 132 arm length values S corresponding to square open loop antennas in upper structural units1And their phase change to reflected light
Referring to fig. 7 and 8, the second super surface structure unit (lower structure unit) includes a second dielectric layer 4 (lower dielectric layer) and a second antenna layer 5 (lower antenna layer). Second oneThe material of the dielectric layer 4 is silicon dioxide. The material of the second antenna layer 5 is the same as that of the second dielectric layer 4 except for the open-ended resonant loop antenna (which is made of metal). Preferably, the metal material is gold. Wherein the thickness d of the lower dielectric layer4420nm, thickness d of the lower antenna layer5150nm embedded in the lower dielectric layer at a distance d from the lower surface of the lower dielectric layer650 nm. Meanwhile, the lower structural unit is of a square structure with the side length T2Is 200 nm. Length L of square split resonant loop antenna2Is 100nm, width W212nm and an arm length of S2. In the present example, the period of the upper structural unit in the y direction is 800nm, which is exactly 4 times the period (200nm) of the lower structural unit in the y direction. Meanwhile, the side length of the upper structural unit is 800nm, which is just 4 times of the side length (200nm) of the lower structural unit, that is, 1 upper structural unit strictly corresponds to 16 complete lower structural units in the xy plane dimension.
When the wavelength of incident light is 650nm, table 2 shows the arm length S corresponding to the square open loop antenna with 128 lower structural units when the phase change of the transmitted light satisfies the parabolic phase distribution2(in Table 2, when S2When the number is positive, the opening is at the upper left corner; s2Negative number, representing its opening at the lower left corner, and its absolute value representing the arm length value). The x coordinate of the central position of the lower structural unit with the number of 1 is-12.7 μm, and the central positions of the following lower structural units are sequentially increased by 0.2 μm. The lower structural units numbered 1, 2 and … … 128 are sequentially arranged along the x-axis direction (namely the x direction) to form a whole row, and the total length of the whole row is 6400 nm; a plurality of such entire rows are periodically arranged in a direction perpendicular to the electric field direction (i.e., y direction) and form a second super surface, the arrangement period is 200nm, and the period number M is 4N.
| Lower structure unit numbering | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| S2(nm) | -56.7 | -80.0 | 30.8 | 49.8 | 72.9 | -35.8 | -52.2 | -75.5 |
| Phase (rad) | 1.96 | 2.99 | 4.01 | 5.02 | 6.02 | 0.72 | 1.69 | 2.65 |
| Lower structure unit numbering | 9 | 10 | 00 | 12 | 13 | 14 | 15 | 16 |
| S2(nm) | 16.5 | 41.6 | 57.2 | -14.9 | -40.0 | -54.6 | -77.4 | 15.4 |
| Phase (rad) | 3.59 | 4.53 | 5.45 | 0.07 | 0.96 | 1.84 | 2.71 | 3.56 |
| Lower structure unit numbering | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 |
| S2(nm) | 39.5 | 53.3 | 73.1 | -30.8 | -45.9 | -59.9 | -82.0 | 15.7 |
| Phase (rad) | 4.40 | 5.22 | 6.03 | 0.54 | 1.32 | 2.09 | 2.84 | 3.57 |
| Lower structure unit numbering | 25 | 26 | 27 | 28 | 29 | 21 | 31 | 32 |
| S2(nm) | 37.6 | 49.6 | 63.3 | -14.9 | -36.1 | -46.6 | -57.2 | -74.2 |
| Phase (rad) | 4.29 | 5.00 | 5.68 | 0.07 | 0.73 | 1.37 | 1.99 | 2.60 |
| Lower structure unit numbering | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 |
| S2(nm) | -81.0 | 22.3 | 37.9 | 47.2 | 55.9 | 68.9 | -15.7 | -31.3 |
| Phase (rad) | 3.19 | 3.76 | 4.32 | 4.86 | 5.38 | 5.88 | 0.09 | 0.56 |
| Lower structure unit numbering | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 |
| S2(nm) | -40.6 | -48.0 | -55.1 | -64.6 | -75.2 | -80.0 | 12.5 | 19.4 |
| Phase (rad) | 1.01 | 1.44 | 1.86 | 2.26 | 2.64 | 3.00 | 3.34 | 3.67 |
| Lower structure unit numbering | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 |
| S2(nm) | 29.4 | 37.1 | 41.6 | 45.9 | 49.8 | 53.3 | 56.4 | 60.7 |
| Phase (rad) | 3.97 | 4.26 | 4.53 | 4.78 | 5.01 | 5.22 | 5.41 | 5.58 |
| Lower structure unit numbering | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 |
| S2(nm) | 65.2 | 68.9 | 72.1 | 75.0 | 76.8 | 78.4 | 79.5 | 80.0 |
| Phase (rad) | 5.74 | 5.87 | 5.99 | 6.09 | 6.16 | 6.22 | 6.26 | 6.28 |
| Lower structure unit numbering | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 |
| S2(nm) | 80.0 | 79.5 | 78.4 | 76.8 | 75.0 | 72.1 | 68.9 | 65.2 |
| Phase (rad) | 6.28 | 6.26 | 6.22 | 6.16 | 6.09 | 5.99 | 5.87 | 5.74 |
| Lower structure unit numbering | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 |
| S2(nm) | 60.7 | 56.4 | 53.3 | 49.8 | 45.9 | 41.6 | 37.1 | 29.4 |
| Phase (rad) | 5.58 | 5.41 | 5.22 | 5.01 | 4.78 | 4.53 | 4.26 | 3.97 |
| Lower structure unit numbering | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 |
| S2(nm) | 19.4 | 12.5 | -80.0 | -75.2 | -64.6 | -55.1 | -48.0 | -40.6 |
| Phase (rad) | 3.67 | 3.34 | 3.00 | 2.64 | 2.26 | 1.86 | 1.44 | 1.01 |
| Lower structure unit numbering | 89 | 90 | 91 | 92 | 93 | 94 | 95 | 96 |
| S2(nm) | -31.3 | -15.7 | 68.9 | 55.9 | 47.2 | 37.9 | 22.3 | -87.0 |
| Phase (rad) | 0.56 | 0.09 | 5.88 | 5.38 | 4.86 | 4.32 | 3.76 | 3.19 |
| Lower structure unit numbering | 97 | 98 99 | 100 | 101 | 102 | 103 | 104 | |
| S2(nm) | -74.2 | -57.2 | -46.6 | -36.1 | -14.9 | 63.3 | 49.6 | 37.6 |
| Phase (rad) | 2.60 | 1.99 | 1.37 | 0.73 | 0.07 | 5.68 | 5.00 | 4.29 |
| Lower structure unit numbering | 105 | 106 | 107 | 108 | 109 | 110 | 111 11 | 2 |
| S2(nm) | 15.7 | -82.0 | -59.9 | -45.9 | -30.8 | 73.1 | 53.3 | 39.5 |
| Phase (rad) | 3.57 | 2.84 | 2.09 | 1.32 | 0.54 | 6.03 | 5.22 | 4.40 |
| Lower structure unit numbering | 113 | 114 | 115 | 116 | 117 11 | 8 | 119 | 120 |
| S2(nm) | 15.4 | -77.4 | -54.6 | -40.0 | -14.9 | 57.2 | 41.6 | 16.5 |
| Phase (rad) | 3.56 | 2.71 | 1.84 | 0.96 | 0.07 | 5.45 | 4.53 | 3.59 |
| Lower structure unit numbering | 121 | 122 | 123 | 124 | 125 | 126 | 127 | 128 |
| S2(nm) | -75.5 | -52.2 | -35.8 | 72.9 | 49.8 | 30.8 | -80.0 | -56.7 |
| Phase (rad) | 2.65 | 1.69 | 0.72 | 6.02 | 5.02 | 4.01 | 2.99 | 1.96 |
Arm length value S corresponding to square open resonant loop antenna in lower structural unit of table 21282And the amount of phase change they impart to the transmitted light.
For the super-surface focusing lens working at the double wavelengths provided by the embodiment of the invention, when x-polarized plane waves with the wavelength of 2365nm irradiate the device, the transparent conductive oxide has a high reflection effect on the device, and meanwhile, the first super-surface is designed to have parabolic phase distribution aiming at the light with the wavelength, so that the light beams can have a good reflection focusing effect. On the other hand, when an x-polarized plane wave having a wavelength of 650nm is irradiated onto the device, the transparent conductive oxide layer 3 has a strong transmission effect on the x-polarized incident light, and thus light of this wavelength band can be irradiated onto the second super surface. Since the second meta-surface has a parabolic phase distribution for light of this wavelength, a beam transmitting focusing effect is produced.
Referring to fig. 9 and 10, through simulation, we obtain the reflected focusing field intensity distribution graph and the normalized intensity distribution curve at the focusing point transversal line of the crossed polarization component (i.e. y-polarized light) of the super-surface focusing lens under the condition of x-polarized incident light with the wavelength of 2365 nm. Fig. 9 shows that a better focusing effect is produced on the side of the reflective space, with a focal length value of 19.4 μm, close to the design value of 20 μm. The white rectangular dotted lines in the figure represent the positions of the super-surface lenses. The normalized intensity profile at the cross-sectional line of the reflective focal spot in fig. 10 shows that the full width at half maximum (FWHM) is 1941nm, less than the wavelength of the operating light, near the diffraction limit, indicating better focusing.
Referring to fig. 11 and 12, transmission focal field strength profiles and normalized intensity profiles at the focal point cross-sectional line for the cross-polarized component (i.e., y-polarized light) for incident light polarized at a wavelength of 650nmx are depicted. FIG. 11 shows that there is a good focusing effect on one side of the projection space, with a transmission focal length value of 19.5 μm, close to the design value of 20 μm. The white rectangular dotted lines in the figure represent the positions of the super-surface lenses. The normalized intensity distribution curve at the focal point cross-sectional line in fig. 12 shows a full width at half maximum (FWHM) of 552nm, also less than the operating wavelength, near the diffraction limit, and also demonstrates a better transmissive focusing effect.
It should be noted that the operating wavelength of the super-surface focusing lens operating at two wavelengths provided by the embodiments of the present invention can be shifted to any set wavelength according to the size scaling effect, as long as the corresponding wavelength is within the selective transmission range of the indium tin oxide material, so as to realize the dual-wavelength operating characteristics in a wider wavelength band range. In addition, the super-surface focusing lens with dual-wavelength work provided by the embodiment of the invention only adopts the super surface based on the plane manufacturing process, so that the super-surface focusing lens has the advantages of simple structure, simple manufacturing process and low manufacturing cost.
[ technical effects ] of
The first super surface and the second super surface can respectively generate electromagnetic response to light with the wavelength of 2365nm and 650nm and focus the light at one point of the reflecting space and the transmitting space respectively. Meanwhile, because the indium tin oxide material has the characteristics of high reflectivity to infrared light and high transmissivity to visible light, when incident light with the wavelength of 2365nm irradiates on the device, the incident light is reflected by the transparent conductive oxide layer 3 (namely the indium tin oxide material), cannot enter the second super surface and only acts on the first super surface, so that the reflection focusing function is realized; when incident light having a wavelength of 650nm impinges on the device, it can pass through the transparent conductive oxide layer 3 (i.e. indium tin oxide material) and act on the second meta-surface, thereby performing a transmissive focusing function. Therefore, the super-surface focusing lens with dual-wavelength operation provided by the embodiment of the invention can realize reflection focusing at 2365nm (belonging to an infrared light wave band, namely a first wave band), namely light is focused on one side of a reflection space; the transmission focusing function is realized at 650nm (belonging to the visible light band, i.e. the second band), i.e. light is focused on one side of the transmission space. The novel dual-wavelength focusing super-surface lens focuses two beams of light with different wavebands in different scattering spaces, simultaneously utilizes a reflection space and a transmission space, has the advantages of simple structure, simple manufacturing process and low manufacturing cost, and simultaneously widens the design idea and application prospect of the super-surface in the aspect of multi-wavelength application.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A super-surface focusing lens, comprising: a first antenna layer, a first dielectric layer, a transparent conductive oxide layer, a second antenna layer, and a second dielectric layer; the first antenna layer is disposed on a first side of the first dielectric layer; a first side of the transparent conductive oxide layer is disposed on a second side of the first dielectric layer; the second antenna layer is embedded inside the second dielectric layer; the second dielectric layer is disposed on a second side of the transparent conductive oxide layer; the transparent conductive oxide layer has a reflectance of 70% or more with respect to incident light in a first wavelength band and a transmittance of 75% or more with respect to incident light in a second wavelength band.
2. The super surface focusing lens of claim 1, wherein the first antenna layer and/or the second antenna layer is a square open resonating ring antenna, a V-shaped open resonating ring antenna, or a circular open resonating ring antenna.
3. The super surface focus lens of claim 1, wherein a first super surface structure unit is composed of said first antenna layer, said first dielectric layer, and said transparent conductive oxide layer; forming a second super-surface structure unit by the second antenna layer and the second dielectric layer; the number of the first super-surface structure units is at least 1 along the direction of the magnetic field component of the light wave, and at least 3 along the direction of the electric field component of the light wave; the number of the second super-surface structure units is at least 1 along the direction of the magnetic field component of the light wave, and at least 3 along the direction of the electric field component of the light wave.
4. The super surface focus lens of claim 1, wherein the material of said transparent conductive oxide layer is a transparent, conductive oxide.
5. The super surface focusing lens of claim 4, wherein the transparent, electrically conductive oxide is indium tin oxide or zinc gallium oxide.
6. The super surface focus lens of claim 1, wherein the material of the first antenna layer and/or the second antenna layer is a metal.
7. The super surface focus lens of claim 6, wherein said metal is gold, silver, aluminum, or copper.
8. The super surface focus lens of claim 1, wherein the material of the first dielectric layer and/or the second dielectric layer is an insulator material or a semiconductor material.
9. The super surface focusing lens of claim 8, wherein the insulator material is silicon dioxide, aluminum oxide or magnesium difluoride.
10. The super-surface focusing lens of claim 8, wherein the semiconductor material is indium phosphide, gallium arsenide, or gallium nitride.
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| CN113325496A (en) * | 2021-05-13 | 2021-08-31 | 中国科学院上海微系统与信息技术研究所 | Sub-wavelength antenna, wavelength-controllable superlens and superlens design method |
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